In the current wireless communication networks, e.g., in the 3rd Generation Partnership Project (3GPP) LTE (long-term evolution) cellular wireless communication network, D2D direct communication is a communication mode in which user equipments with TDD mode enabled cellular transceivers directly make peer-to-peer (P2P) communication by sharing/reusing wireless link (Uplink or Downlink) resources of the cellular communication network. In D2D direct communication, there is a plurality of channel access schemes for D2D user equipments to access the wireless communication channels. For example, RTS (Request To Send)/CTS (Clear To Send) supplemented Carrier Sensing Multiple Access/Collision Avoidance (CSMA/CA) as a typical channel access scheme used in most ad-hoc network collaborates with the cellular wireless communication system to enable access and direct communication of D2D user equipment in the cellular environment. For better understanding of the present invention, a channel access mechanism of RTS/CTS-based D2D user equipment is introduced briefly as follows.
When one D2D user equipment (transmitter) intends to transmit a packet to a peripheral another D2D user equipment (receiver), it first transmits RTS packet to request a data channel via a control channel. If there is an idle data channel, the receiver replies with a CTS packet. After the transmitter receives the CTS packet successfully, it proceeds to transmit the actual data packet. Other D2D user equipments in the same area, after hearing the RTS packet transmitted by the transmitter, will defer transmission of their own RTS packets to allow the transmitter to have a sufficiently tong period of time to receive the CTS packet transmitted by the receiver as a response. Other D2D user equipments upon hearing the CTS packet will back off transmission of RTS packet for a period of time that is sufficiently long to allow the receiver to receive the entire data packet, thereby enabling direct communication between the D2D user equipments without interference of nearby D2D user equipments. In such hybrid environment of D2D and cellular communications, resources will be allocated to control channels and data channels for communication. Take RTS/CTS access scheme as an example, the dedicated resources are allocated for RTS/CTS transmission so as to ensure the D2D control channels with RTS/CTS transmit without interference of other channels, and the resources of the corresponding data channels can be shared or reused between D2D and cellular communications.
However, some existing problems in such hybrid D2D and cellular networks are reducing system efficiency. First of all, with regard to resource division, resources in D2D direct communication and cellular communication must be divided reasonably in order to obtain efficient resource sharing/reusing. In the event of unreasonable resource division, for example, if the reserved resources for D2D direct communication are overestimated, it will waste the scare frequency resource and likely degrade the cellular communication performance. On the other hand, the underestimated resource for D2D direct communication would lead to the congestion on D2D access, degrading D2D direct communication performance.
Therefore, how to make efficient resource allocation, particularly how to reasonably allocate resources for D2D direct communication is crucial for acquisition of efficient resource sharing/reusing. Currently, the allocation of communication resources of D2D user equipment and cellular user equipment is typically based on the some static parameters settings. For example, with 10 MHz LTE Uplink frequency band, 2 MHz can be allocated for D2D communication and the remaining 8 MHz is allocated for cellular communication. Obviously such resource division is not suitable for a dynamically changing communication environment as being relatively fixed and thus lacking flexibility and adaptation.
Secondly, with regard to interference problem, since RTS/CTS supplemented CSMA/CA can effectively reduce interference among D2D user equipments, the current D2D user equipments are mainly experiencing two types of interference depending on positions thereof: intra-cell cellular interference and inter-cell cellular interference. When the D2D user equipment is located in the cell edge, resource reusing with cellular user equipment at the edge of the neighbor cell may suffer from the strong co-channel cellular interference due to the high power of communication transmission of the cellular user equipment.
Therefore, in the event of D2D direct communication by virtue of reusing/sharing the uplink resources, how to reduce interference from cellular user equipments, particularly reduce interference from cellular user equipments in the neighbor cell is of most importance for improving D2D direct communication performance. Currently, there is no desirable solution to this problem.